Reversible pressure hydraulic system



NOV. 1966 E. A. ROESKE REVERSIBLE PRESSURE HYDRAULIC SYSTEM Filed Nov. 13, 1964 United States Patent 3,286,635 REVERSIBLE PRESSURE HYDRAULIC SYSTEM Eugene A. Roeske, St.'L0uis, Mo., assignor to Borg- Warner Corporation, Chicago, 111., a corporation of Illinois Filed Nov. 13, 1964, Ser. No. 410,847 1 Claim. (Cl. 103-3) discharge port, without reversing the rotation of the shaft driven by a powersource. However, the system according to the present invention also operates if the shaft rotation is reversed.

In the preferred form of the present invention the flow of fluid is reversed by reversing the swash plate angle when the system is .providedwith a piston pump, and by reversing the cam ring eccentricity when the system is provided with a vane pump.

It is therefore an important object of the present invention to provide an improved reversible flow pressure controlled hydraulic system having control means whereby a predetermined constant fluid pressure 'is maintained.

It is still another import-ant object of the present invention to rovide a piston pump in an improve dhydraulic system which serves to reverse the flow of fluid when the swash plate angle is reversed.

It is still a further object of the present invention to provide a vane pump in an improved hydraulic system whereby the flow of fluid is reversed by reversing the cam ring eccentricity.

The present invention consists of the novel constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above objects and such other objects as will be apparent from the following description of preferred forms of the present invention, illustrated with reference to the accompanying drawings, wherein:

FIGURE 1 is a schematic illustration of a reversible pressure hydraulic system according to the present invention wherein a vane pump is the source for providing fluid under pressure, and;

FIGURE 2 is an illustration in fragment of a piston pump incorporating the port plate shown in FIGURE '1.

In the hydraulic system according to the present invention shown schematically by FIGURE 1, there is shown schematically a vane pump 10 which serves as a source of fluid supply under pressure, comprising a shaft 10a connected to a rotor 11 provided with vanes 12 operable Within a housing 13 having a cam ring 14 therein. The cam ring 14 is slidedly mounted in the housing 13, whereby when the cam ring 14 is moved from its eccentric position in one direction to its eccentric position in the opposite direction, the fluid flow is reversed. Suitable reversible means 14a are provided for this purpose. A rotatable port plate 15 is shown which for the sake of clarity and convenience is disassociated with respect to the vane pump 10 of which it is a part. The rotatable port plate 15 is provided with a pair of kidney ports 16 and 17 connected to fluid passages 18 and 19, respectively, which serve as either intake or exhaust ports, depending on the eccentricity position of the cam ring 14.

A hydraulic fluid pressure control means 20, for maintaining a predetermined constant fluid pressure, is in fluid communication with the vane pump 10 by means of a fluid passage 21 which in turn is connected to fluid passages 22 3,286,635 Patented Nov. 22, 1966 Ice and 22a which are interconnected to fluid passages 18 and 19, respectively. A pair of check valves 23 and 24 are provided in the fluid passages 22 and 22a, respectively, and are oriented so as to permit fluid flow only in a direction from these passages thereby serving to provide a closed line for the passage of fluid to the present control means 20 regardless as to whether or not the fluid flows frornpassages 18 or 19. I

To illustrate, if the cam ring 14 is in the direction of eccentricity with respect to the rotor 11, as shown in the drawing, and the kidney port 16 is the exhaust port, fluid will flow through the fluid passage 18 into the fluid passage 22, through the check valve 24 into the fluid passage 21 and thence into the hydraulic fluid pressure control means 20. The check valve 23, of course, will close under these conditions. If the cam ring 14 is moved to its eccentricity position in the opposite direction the kidney port 17 will become the exhaust port and fluid will flow through the fluid passage 19 into the fluid passage 22a, through the check valve 23 and into the fluid passage 21 and thence to the hydraulic fluid pressure control means 20. The check valve 24, of course, in this instance will be closed.

The hydraulic fluid pressure control means 20 comprises a spool valve 25 provided with a cylindrical chamber 26 having a spool 27 operable therein that is provided with a fluid passage 28 which is in fluid communication at one end thereof with the fluid passage 21, and at the other end thereof communicable with ports 30 and 31 connected to fluid passages 32 and 33, respectively. The ports 30 and 31 are operably communicable with ports 34 and 35, respectively, which are provided 'withfluid passages 36 and 37, respectively, connected to a sump 38. A spring 39 is biased between one end of the spool 27 and the end of the cylindrical chamber 26 urging the spool 27 in a direction toward the fluid passage 21.

The hydraulic fluid pressure control means 20 also includes a cylinder 40 which has a piston 41'operable therein'operably connected to an arm 42 of the rotatable port plate 15 by means of a piston rod 43.

In FIGURE 2 a piston pump 44 is shown which may be used as an alternate for the vane pump 10. The piston pump 44 is driven by a shaft 44a connected to a source of power and comprises a housing 45 having cylinders 46 therein provided with pistons 47 which are actuated by a wobble plate 48. A'suitable reversible means 49 connected with respect to said wobble plate 48 is provided for reversing the angle of the said wobble plate 48 which changes the direction of fluid flow.

In'operation when the kidney port 16 is wide open and serves as the exhaust port and the pressure'exceeds the value of spring 39 as shown in the drawing, fluid passes through the fluid passage 18 into the fluid passage 22 through the check valve 24 and into the fluid passage 21 and thence into the cylindrical chamber 26. Pressure is exerted against the adjacent end of the spool 27 and if it exceeds the value of spring 39 the spool 27 takes the position as shown in the drawing thereby exposing the port 31 and permitting fluid to pass through the fluid pas sage 33 into the cylinder 40 at the piston side thereby causing the piston 41 to move the rotatable port plate 15 in a direction which reduces the volume of fluid pumped and hence the pressure to the value of the spring 39. Under these conditions the fluid on the rod side of the cylinder 40 passes through the fluid passage 32, the port 30, the port 34 and thence into the sump 38.

It therefore can be seen that the value of the spring 39 determines the fluid pressure in the system. When the pressure in the system has reached the value of the spring 39 the position of the spool 27 is such with respect to the ports 30 and 31 and the position of the piston 41 that the volume of fluid pumped through the adjusted position of the kidney exhaust port 16 is such that the fluid pressure is in balance with the value of the spring 39.

When the flow of fluid is reversed by moving the cam ring 14 to its opposite eccentric position, the kidney port 17 becomes exhaust port and fluid then is delivered by way of fluid passage 19, fluid passage 22a through the check valve 23 and thence into the fluid passage 21 and into the cylindrical chamber 26. The check valve 24 in this instance would be closed.

It is therefore apparent that regardless as to the direction of fluid flow the hydraulic fluid pressure control means 20 functions the same. In the event the pressure in the system is below the value of the spring 39 the spool 27 moves in a direction whereby the port 30 is exposed to the fluid passage 28 and closed with respect to the port 31 and the piston 41 in this instance, of course, would be moved by the rotatable port plate 15 in a direction which would increase the volume of fluid pumped and therefore under those conditions, fluid passes through the fluid passage 28, through the port 30 into the fluid passage 32 and thence into the cylinder 40, on the rod side, and the fluid on the piston side would pass through the fluid passage 33, the port 31, the port 35 and thence into the sump 38. 7

While this invention has been described in connection with certain specific embodiments thereof, it is to be understood that is by way of illustration and not by way of limitation and the scope of this invention is defined solely by the appended claim which should be construed as broadly as the prior art will permit.

I claim:

A reversible flow pressure controlled hydraulic system comprising:

(a) a reversible variable displacement hydraulic pump wherein the flow of fluid may be reversed without reversing the sense of rotation, comprising:

(1) a housing,

(2) fluid pumping means operable in said housing,

(3) a rotatable port plate associated with said pumping means,

(4) first and second kidney ports associated with said rotatable port plate,

(5) first and second fluid passages connected to said first and second kidney ports, respectively,

(6) first and second check valves in said first and second fluid passages, respectively,

(7) a third fluid passage connected to said first and second fluid passages between said first and second check valves whereby, regardless of the direction of fluid flow, the fluid is discharged through said third fluid passage, and

(8) means for rotating said rotatable port plate,

(b) a source of power connected to said reversible displacement hydraulic pump for driving said pump,

(c) reversible means connected with respect to said pump for reversing fluid flow,

a cylinder having a piston operable therein provided with a piston rod operably connected to said rotatable port plate thereby serving to regulate the volume of fluid pumped,

a spool valve comprising:

(1a) a cylindrical chamber,

(2a) a spool operable in said cylindrical chamber,

(3a) -a first port in said cylindrical chamber in fluid communication with the rod side of said cylinder,

(4a) a second port in said cylindrical chamber in fluid communication with the piston side of said cylinder,

(5a) a third port in said cylindrical chamber communicable with a sump and said first port,

(6a) a fourth port in said cylindrical chamber communicable with said sump and said second port,

(7a) a fourth fluid passage communicable with said first and second ports and in com munication with one end of said cylindrical chamber and (8a) a spring biased between the other end of said cylindrical chamber and the said spool, the said third fluid passage being connected to the said one end of said cylindrical chamber whereby fluid is delivered to the said spool valve regardless of the direction of fluid flow from the said pump, which in turn provides fluid to said cylinder for the operation of said piston for controlling the movement of said rotatable port plate thereby controlling the volume of fluid pumped which in turn determines the fluid pressure level based on the value of said spring.

References Cited by the Examiner UNITED STATES PATENTS 2/ 1953 De Lancey et a1.

6/1953 Born et a1. 103-3 X 4/ 1957 Jeannin.

8/1958 Gondek 1033 5/1963 Firth et al. 103-162 3/1965 Smithson 103-162 9/1965 Potter et al 103-l62 X MARK NEWMAN, Primary Examiner. SAMUEL LEVINE, Examiner.

W. L. FREEH, Assistant Examiner, 

